Lake Ontario-St. Lawrence River Water Levels Update at the Onset of Winter


The International Lake Ontario-St. Lawrence River Board is providing this notice to summarize the water level conditions as winter approaches.  As a reminder, Plan 2014 is a set of rules that govern Lake Ontario outflows through the Moses-Saunders Dam located between Massena, New York and Cornwall, Ontario. 

  1. Lake Ontario’s water levels had been above long-term average during the spring, summer, and early fall of 2023.  Water levels in the lake reached and remained near long-term average the last week of October and first week of November 2023. Since then, the water levels of Lake Ontario have decreased slightly below the long-term average.  
  2. Water levels at Lake St. Lawrence, the forebay of the Moses Saunders Dam, were below long-term average since spring, which was to be expected as the outflows prescribed by Plan 2014 remained above-average.  Being directly upstream of the hydropower dam, the forebay experiences more immediate and pronounced water level changes because of dam operations.  When outflows through the dam are increased, water levels in the Lake St. Lawrence forebay decrease.  During the holiday weekend in October, strong southwesterly winds caused water levels in the forebay to increase above the long-term average. Since then, Lake St. Lawrence water levels have generally remained below the long-term seasonal average. In the spring, the Board will resume sharing the water level forecast for Lake St. Lawrence and continue to do so throughout the recreational boating season.
  3. Water levels in the lower St. Lawrence River had been near or above long-term average during summer 2023 and since then have experienced their expected seasonal decline.
  4. Please read the water levels update issued October 26, 2023, for a summary of deviations that occurred from September 2 through November 17, 2023.
  5. From November 18 through December 1, outflows returned to the Plan 2014 Rule Curve.
  6. As of December 2, L Limit  within Plan 2014 took effect. The L Limit defines maximum Lake Ontario outflows that ensure safe operating conditions (i.e. adequate water levels and safe currents) for commercial navigation and other vessels in the upper St. Lawrence River. 
  • ​​​​​​According to the U.S. Army Corps of Engineers, The Soo Locks’ will close January 15, 2024, or until commercial traffic ceases, whichever occurs first.
  • The Seaway Notice announced the Montreal-Lake Ontario section of the Seaway is projected to close on January 5, 2024, and the Welland Canal section is expected to close on January 7, 2024.
  • Commercial shipping on the St. Lawrence River from the Port of Montreal downstream continues through the winter.

       7. I Limit Rules may take effect throughout the winter months. The Plan 2014 I Limit rules set maximum outflows to help facilitate the formation of a safe, stable ice cover in the river. 

For more information on:


United States:



The International Lake Ontario-St. Lawrence River Board ensures that outflows from Lake Ontario meet the requirements of the International Joint Commission’s Orders of Approval. Under any regulation plan, the ability to regulate the outflow from Lake Ontario does not mean that full control of lake levels is possible. This is because the major factors affecting water supply to the Great Lakes - precipitation, evaporation, and runoff - cannot be controlled, and are difficult to accurately predict.